Conclusion
PHC host materials for simplified PhOLED devices

The various examples of host matrices presented in this article lead to the conclusion that PHC host matrices represent a new generation of matrices with great potential for the development of PhOLEDs. These PHC matrices, free of heteroatoms, are built solely on benzene rings assembled by different linkages enabling their energy levels to be modulated. Most of these matrices feature a wide HOMO/LUMO gap, a high triplet state energy level and good thermal and morphological stabilities. Despite low charge carrier mobilities, a few recent examples have shown that ambipolar character can be achieved with PHCs, which is a considerable advantage for promoting electron-hole recombination in the center of the device.